NEEDHAM — In the first televised tussles of the Senate special election campaign, Representatives Edward J. Markey and Stephen F. Lynch, the two Democrats in the race, tangled over health care and abortion, defending their role in Washington gridlock, while Republican hopefuls Gabriel Gomez, ­Michael Sullivan, and Daniel Winslow, sought to intro­duce themselves to voters in their own fast-moving, half hour-matchup.

The debates, held back-to-back on several local television stations, offered candidates in both primaries a chance to reach out to voters who have yet to become engaged in the quiet special election race to succeed Senator John F. Kerry, with barely a month to go ­before the April 30 primaries.

On the Democratic side, Markey cast himself as an experienced lawmaker and liberal successor to Massachusetts senators Kerry and Edward M. ­Kennedy, while Lynch, a onetime ironworker, positioned himself as a populist fighter unafraid to buck party leadership.

In a preceding debate between the three lesser-known Republicans — also organized by a consortium of Boston media — the GOP hopefuls were quicker to challenge the two Democratic candidates than each other. They disagreed on some social issues and on policy nuances, but sounded similar themes about the need for balanced budgets, smaller government, and fewer regulations, while appealing for ­Massachusetts to send a new face to Washington.

Early questions from moderator R.D. Sahl to Democrats zeroed in on Lynch’s votes against President Obama’s health care overhaul legislation in 2010 and his self-described prolife status, positions that put him outside a Democratic establishment that has coalesced behind Markey.

But Lynch, who said he respects Roe v. Wade, defended his votes as a reflection of an independent streak and pressed Markey for supporting NAFTA and a Wall Street bailout without doing enough for Massachusetts fishermen.

Markey called his own vote in favor of Obama’s health care legislation “the proudest vote of my career,” helping to ­extend coverage to tens of millions of previously uninsured Americans. He also called it a defining cause of Democrats “from Harry Truman through Ted Kennedy” and a bright line dividing the parties.

“Steve, when that vote came up, you were wrong when you were needed most,” Markey said. “That was the ­only option we had to support President Obama and to put that bill on the books.”

Lynch said the legislation gave up too much to insurance companies to get them to drop their fight while imposing taxes that he said would harm middle-class workers and local businesses.

“It was like a hostage situation where we not only paid the ransom. but we let the ­insurance companies keep the hostages,” said Lynch, a 57-year-old from South Boston. He called himself proud to stand up at times to party leaders.

“Hey, I don’t work for ­Nancy Pelosi, and I won’t work for Harry Reid,” he said.

The Democrats also jousted on the Wall Street bailout: Lynch called it a sop to banks; Markey said it was necessary to prevent another Great ­Depression. But they agreed on the need to keep interest rates low and for tough sanctions against Iran.

In the Republican match-up, all three GOP candidates indicated they would repeal the president’s health care plan, arguing that Massachusetts had already addressed the ­issue of universal coverage, but they also said they would repeal the Defense of Marriage Act that prevents the federal government from recognizing state-approved same-sex marriages and that is now before the US Supreme Court.

Jim Davis/Globe Staff

Democrats Stephen F. Lynch (left) and Edward J. Markey had a brief handshake after the debate.

Gomez said two people in love “should be able to get married,” and state Representative Daniel Winslow, a former judge and legal adviser to Governor Mitt Romney, declared support for “equality of marriage for all people in Massachusetts and the country.” Sullivan, a former US attorney, said he would defer to states on marriage.

For the Republicans, the Wednesday night matchup represented the first televised opportunity to get their message out to a wider audience. A WBUR-FM poll released this week showed that even among likely Republican voters, 60 percent had not heard of Winslow, 47 had not heard of Gomez, and 34 percent did not know Sullivan.

Winslow, with experience as a litigator, appeared most comfortable before the camera and even squeezed in a plug for viewers to check out his campaign website.

Sullivan played the role of unexcitable senior statesmen, a former state legislator and Plymouth County district ­attorney who became the state’s top federal prosecutor and then director of the US Bureau of Alcohol, Tobacco, Firearms, and Explosives under President George W. Bush. The most conservative of the three on social issues, Sullivan challenged Gomez on experience and jabbing at his wealth as a private investor, asking him to describe the largest budget he has managed — besides his own.

Gomez said he had been in the business of investing in companies small, medium, and large and had sat on the board of a large company, responsible for managing a budget of more than $3 billion.

He also cited his experience as a pilot and Navy SEAL, as well as his private sector work, and said, “I’ve got leadership experience and I’ve been effective my whole life.”

But, given an opportunity to challenge his two Republican opponents with a question, Gomez, the least-tested of the three candidates, took a pass. “I’m not here to ask questions of my fellow candidates, to try to tear them down or put them on the spot,” Gomez said, instead posing a rhetorical question to the unseen Democrats who would soon follow on the Channel 5 stage.

The Republicans addressed a large swath of topics, offering glimpses of their positions on abortion and how they would balance the federal budget.

The WBUR poll found that Sullivan led his two opponents on the Republican side, while Markey was leading Lynch in the race for the Democratic nod. Both Markey and Lynch were still seen as likely to beat any of the Republicans in a direct matchup.

Eric Moskowitz can be reached at emoskowitz@globe.com. Martin Finucane of the Globe staff contributed to this report.

Clarification: An earlier version of this story failed to make clear that the debates in the special election for Senate were broadcast on several television stations, among them WCVB-TV,WGBH-TV, WHDH-TV and NECN.

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